1. Field of the Invention
This invention relates to storing material. The material may be one or more of video material, audio material and data material.
2. Description of the Prior Art
Reference will be made in the following to video material for convenience. However the invention is not limited to video material. It may be applied to audio material. It may be applied to data material other than audio and video. It may be applied to material having one or more components selected from audio, video and data material.
It is known to identify video material by applying a “watermark” to the video signal. A watermark is a coded signal, which is combined with the video signal in such away that the coded signal is invisible or substantially invisible in the displayed image. The coded signal is detectable in the video signal: it is used for detecting infringement of copyright for example. However, watermarks may be damaged or removed deliberately or inadvertently by further processing of the material e.g. by editing or applying special effects. Also, there may be a perceived fear that applying a watermark may cause a deterioration, however small, in the video signal.
Recently it has also been recognised that associating so-called metadata with material can provide a powerful means of handling, indexing and using material. In GB-A-2 361 136 for example, the metadata is provided in a database, with entries in the database being linked to the material by means of a material identifier such as an SMPTE Unique Material Identifier (UMID). The UMID itself is coded into the material in a watermarking arrangement.